From 2d2ff221926bb11bfe5d544dc1fbd558fab89f10 Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Mon, 15 Nov 2021 15:19:40 -0500
Subject: [PATCH] pick the right share to use for lease renewal decisions
now that the server actually returns different info for different shares, we
can, and we should, and we must
---
src/_zkapauthorizer/lease_maintenance.py | 25 +++++++++++++++++++++---
1 file changed, 22 insertions(+), 3 deletions(-)
diff --git a/src/_zkapauthorizer/lease_maintenance.py b/src/_zkapauthorizer/lease_maintenance.py
index 8858c91..e8e76cd 100644
--- a/src/_zkapauthorizer/lease_maintenance.py
+++ b/src/_zkapauthorizer/lease_maintenance.py
@@ -206,12 +206,31 @@ def renew_leases_on_server(
# Keep track of what's been seen.
activity.observe([stat.size for stat in stat_dict.values()])
- # All shares have the same lease information.
- stat = stat_dict.popitem()[1]
- if needs_lease_renew(min_lease_remaining, stat, now):
+ # Each share has its own leases and each lease has its own expiration
+ # time. For each share the server only returns the lease with the
+ # expiration time farthest in the future.
+ #
+ # There is no API for renewing leases on just *some* shares! It is
+ # all or nothing. So from the server's response we find the share
+ # that will have no active lease soonest and make our decision about
+ # whether to renew leases at this storage index or not based on that.
+ most_endangered = soonest_expiration(stat_dict.values())
+ if needs_lease_renew(min_lease_remaining, most_endangered, now):
yield renew_lease(renewal_secret, cancel_secret, storage_index, server)
+def soonest_expiration(stats):
+ # type: (Iterable[ShareStat]) -> ShareStat
+ """
+ :return: The share stat from ``stats`` all the leases of which will expire
+ soonest.
+ """
+ return min(
+ stats,
+ key=lambda stat: stat.lease_expiration,
+ )
+
+
def renew_lease(renewal_secret, cancel_secret, storage_index, server):
"""
Renew the lease on the shares in one storage index on one server.
--
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